from socket import *

host = '127.0.0.1'
serverPort = 21

serverSocket = socket(AF_INET, SOCK_STREAM)
serverSocket.bind((host, serverPort))
serverSocket.listen(5)
connectionSocket, addr = serverSocket.accept()
data = connectionSocket.recv(1024)

if data:
    connectionSocket.send('OK'.encode())
    print("send success")